1. Field of the Invention
The present invention relates to an electron emission device, and more particularly, the present invention relates to an electron emission device which has driving electrodes arranged perpendicularly to each other while interposing an insulating layer.
2. Description of Related Art
Generally, electron emission devices are classified into those using hot cathodes as an electron emission source, and those using cold cathodes as the electron emission source. There are several types of cold cathode electron emission devices, including a Field Emitter Array (FEA) device, a Metal-Insulator-Metal (MIM) device, a Metal-Insulator-Semiconductor (MIS) device, and a Surface Conduction Emitter (SCE) device.
The FEA electron emission device is based on the principle that when a material having a low work function or a high aspect ratio is used as an electron emission source, electrons are easily emitted from the electron emission source when an electric field is applied thereto under the vacuum atmosphere. A sharp-pointed tip structure based on molybdenum (Mo) or silicon (Si), or a carbonaceous material such as graphite has been used in forming electron emission regions.
In an FEA electron emission device, electron emission regions are formed on a first substrate together with cathode and gate electrodes functioning as the driving electrodes for controlling the electron emission. Phosphor layers are formed on a second substrate together with an anode electrode for accelerating the electrons emitted from the electron emission regions toward the phosphor layers. An insulating layer is disposed between the cathode and the gate electrodes to insulate them from each other, and the cathode and the gate electrodes are stripe-patterned and are perpendicular to each other.
With the above structure, the insulating layer can be formed with a small thickness of 10 micrometers to make micro-pixels. However, with the FEA electron emission device having an insulating layer of such a thickness, the surface of the insulating layer is rough depending upon the outline of the cathode electrodes. When a metallic material is deposited on the surface of the insulating layer to form gate electrodes, the gate electrodes also have a rough surface depending upon the surface state of the insulating layer.
Like the above, when the gate electrodes do not have a flat surface but rather have a rough surface, cracks are easily formed on the lateral edge of the gate electrode at the crossed region thereof with the cathode electrode. The cracks are propagated to the center of the gate electrode to locally increase the resistance of the gate electrode, and can even cause the breaking of the gate electrode. Such a problem becomes more serious as the thickness of the insulating layer is reduced.